1. Field of the Invention
This invention relates to a termination device for switchgear and more particularly to a drawout terminal block tray for housing external instrumentation and control wiring of a circuit interrupter.
2. Background of Information
Low voltage switchgear, which has a maximum power line voltage of 600 VAC, is generally mounted in an enclosure which houses up to four circuit interrupters. Power cables for the circuit interrupters are generally terminated in the rear of the enclosure. Instrumentation and control terminal blocks for the circuit interrupters, which have a nominal control voltage of 120 VAC, may either be mounted in the rear or the front of the enclosure.
Drawout circuit breakers or drawout circuit interrupters may be completely removed from the front of the enclosure for repair, testing or maintenance. Because of this drawout mode of operation, the instrumentation and control terminal blocks may either be mounted in the rear of the enclosure, which does not interfere with the drawout removal of the circuit breakers, or the terminal blocks may be mounted away from the drawout path of the circuit breakers in the front of the enclosure. Front mounting of terminal blocks with drawout circuit breakers, thus, requires that individual portions of the front surface of the enclosure be dedicated to either, but not both of, the drawout circuit breakers or the terminal blocks. Therefore, the front surface area of the enclosure is at a premium and must be carefully allocated.
Whenever the instrumentation and control terminal blocks are mounted in the rear of the enclosure, special barriers are typically provided to ensure the integrity of the wiring design and to protect instrumentation and control service personnel from the higher switchgear voltages.
On the other hand, if the instrumentation and control terminal blocks are mounted in the front of the enclosure, two options are possible. One or more circuit interrupters may be removed from the enclosure and moved to a separate enclosure, in order to provide space for mounting the instrumentation and control terminal blocks. Otherwise, one or more separate instrumentation and control enclosures are provided for housing the terminal blocks. Although front mounting generally improves the wiring design integrity, enhances the safety of service personnel, and reduces the length of the wiring, the cost of providing the additional enclosures and the requisite floor space for such enclosures is a substantial disadvantage.
There is a need, therefore, for a compact front-access termination device which accommodates the external instrumentation and control wiring of a circuit interrupter.
There is a more particular need for such a termination device that is located in an enclosure which houses the circuit interrupter.
There is an even more particular need for such a termination device that presents the floor space required by the enclosure and permits the same number of circuit interrupters to be housed by the enclosure.